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Wilderness Tripping - BWCA & Beyond New Topic Printer Friendly Version

  kevlar vs fibre glass?
  Posted by: Dr1Gonzo on Jul-23-13 1:30 PM (EST)
 

To date, I've always used the fibre glass canoes but the kevlar ones seem better when there is a lot of portage involved.
The guy at the renmtal shop said the kevlar wa smore fragile but I had always assumed it would be stronger?
Is it just that it can puncture more easily on rocks?

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  None of the above
  Posted by: pblanc on Jul-23-13 5:40 PM (EST)
How strong or fragile a canoe is depends not only on the materials but the layup schedule. You can't really make sweeping generalizations. Canoes made of all fiberglass tend to be somewhat brittle compared to those made using composite fabrics.

Relatively few canoes are made using only aramid (Kevlar) these days. Mad River made some all Kevlar gel-coated boats back in the 1980s. I own two and they have proven to be quite strong indeed.

A better choice is to use a combination of materials. Aramid is generally used on the interior of canoes and it is quite puncture resistant. In fact, with boats that have fiberglass on the exterior and aramid on the interior the fiberglass will often crack or tear and the aramid remain intact (but delaminated from the 'glass layers. The best boats combine aramid for the interior layers along with either S fiberglass or carbon fiber fabric on the exterior.

"Fiberglass" boats often incorporate other fabrics into the layup schedule like polyester or nylon. Spectra (a fabric made out of polyethylene fibers) and Dynel are also sometimes used. Incorporating these fabrics into a canoe made primarily of fiberglass can reduce brittleness.
 
 
  strength of canoes
  Posted by: ppine on Jul-24-13 2:25 PM (EST)
Modern boats have done a much better job of using materials effectively for strength while saving weight.

I have had many fiberglass boats and one early Kevlar boat. It was a Sawyer Charger 18 1/2 feet long. It was made in 1978 and eventually started to fall apart literally. I fixed it with cloth and epoxy but it was never right after that.

All kevlar and fiberglass boats can be crunched beyond repair with a simple wrap around a rock. Always remember that.
 
 
  Generally speaking
  Posted by: jackl on Jul-25-13 6:24 AM (EST)
kevlar is lighter but more delicate then fiberglass.
Note that I said generally speaking

Jack L
 
 
  relative strengths
  Posted by: plaidpaddler on Jul-26-13 11:07 AM (EST)
As pblanc said, strength is as much dependent on the layup and construction as it is on the type of cloth. In general usage a good quality Kevlar layup is no more delicate than a quality fiberglass layup. It can be much lighter to carry. In my usual reference hull, the 17'Wenonah Spirit; the lightest Kevlar layup is in the 40#range. The fiberglass hull using the same construction was around 50#. The less expensive layup in fiberglass was in the 65#range. Wenonah has used , different layups in this hull over the years. Core-stiffened, now called ultra-iight; cross-rib, center-rib,and extra-stiffened. They made all but extra-stiffened in both fiberglass and Kevlar. lots of different constructions and differing weights and strengths.
If you could lift it, the least expensive extra-stiffened fiberglass version was the most puncture resistant. It had so many layers of cloth in the hull bottom. I have paddled a cross-rib Kevlar hull for almost 30 years now and it has seen a lot of rough usage. The bottom of the bow has multiple repair areas of epoxy putty from rock impacts. The damage in all cases was just the gel-coat layer being gouged by the rock. The Kevlar cloth beneath has fuzzed from the impact, but never yielded. Several accidents have flexed the bottom so severely that two ribs have been separated from the hull. But the Kevlar hull has not torn or punctured, only the resin has cracked. All the accidents were repaired by securing the ribs with new layers of cloth and resin. This hull flexes under impact. Going over a submerged log you can see the bottom flex upward as the log passed under the canoe. It then returns to shape. The hull has many scratches from these encounters, but is intact. I can not say that this Kevlar hull is delicate. It is as strong as the fiberglass version of this layup, it is just more expensive and is 12# lighter.
Impacts are an "if" factor, portages are a reality. Never once have I wished I had bought the tuff-weave version instead of Kevlar. Several times at the top of the Raquette Falls Portage, I wished I had the ultra-light version,but never the royalex.
Bill
 
 
  Note that I said "generally" Bill
  Posted by: jackL on Jul-28-13 6:55 AM (EST)
My experience has been much like yours and I would much prefer a kevlar canoe to a fiberglas one, but we put a hole in our comp cruiser bow once that I doubt would have come through a fiberglass canoe

Jack L
 
 
  Comp cruiser not good comparison
  Posted by: plaidpaddler on Jul-28-13 11:03 PM (EST)
Jack,
If you had the available clear glass layup on your comp cruiser, it still would have holed on the same object. The comp boats are no where as strong as the rec canoes. The bows are especially sharp and that makes them weaker in any fabric. Logic for race boats are that they are paddled by experts looking for lightest weight and fastest hull speed. Durability is secondary. And for years the really fast paddlers got new boats from the factory every year to keep that slight edge over the other paddlers. In the top rank of marathon paddlers a difference of 0.01 mph is 52.8 feet every hour. Over six hours that's over 300 feet which is huge. In our classes, First to Third place might be a difference of 30 minutes with teams in the same model canoe.
Bill
 
 
  Which forum to use?? Your guess.
  Posted by: g2d on Aug-01-13 2:46 PM (EST)
 

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